1. Field of the Invention
The present invention is related to communications systems and more particularly, to digital communications systems such as VoIP telecommunications systems.
2. Background Description
Commercial telecommunications platforms have allowed service providers to deliver Internet Protocol (IP) based telecommunications services. Typical such IP telecommunications services feature common channel telecommunications packet switching capabilities, such as Signaling System Number 7 (SS7) signaling capabilities. These capabilities allow for legacy feature support and, further, interconnection with Public Switched Telephone Networks (PSTN). Digital communications such as Voice over IP (VoIP), for example, normally use Session Initiation Protocol (SIP) for establishing and clearing of connections between network stations. VoIP calls using SIP work well for a relatively simple connection with simple user control, e.g., using a typical user interface.
However, some complex features have proven difficult to implement in VoIP using SIP, regardless of the user interface. For example, SIP has no provision for handling calls directed to unavailable locations, or calls forwarded to restricted access locations. Instead, these may be handled by the network communications server, on an ad hoc basis with spotty results. Unfortunately, such calls have a high likelihood of occurrence.
Thus, there is a need for flexibly adding features to Session Initiation Protocol (SIP) based systems and, more particularly, for a simple efficient way to add features, even complex features, to existing Voice over IP (VoIP) systems.